CRANKCASE PROBLEM

twinegar · Post by **twinegar** » Fri Aug 28, 2009 1:44 pm

I mentioned in another post that my starter is whining and now not engaging the engine. I just dropped the engine forward and removed the starter and discovered that the front bolt hole that the starter bolts into is broken away. I wonder if the hole could be drilled deeper and threaded to hold a longer bolt. Any suggestions? I would hate to have to replace the upper case because of this. I should have walked away from the deal when I heard the starter whining but it is too late now.

Terry · Post by **Terry** » Sat Aug 29, 2009 2:13 am

I had my starter out 2-3 times before I realized the problem was the starter clutch. You do know the motor doesn't have to be tilted or moved to remove the starter don't you? I'd sure try to fix that hole before tackling a motor swap of all the internals into another set of cases. Talk to an expert welder/mechanic maybe?

EMS · Post by **EMS** » Sat Aug 29, 2009 10:43 am

I think the case beind the hole is shaped such that if you drill the hole deeper, you will drill partially out in the air. I doubt there is enough material to make a good thread.

twinegar · Post by **twinegar** » Sat Aug 29, 2009 11:02 am

I only tilted the engine so I could get a clear picture of what was up. I also pulled the starter from another CBX and stuck it in and got the same whining sound so I am guessing that a previous owner stuck something under the starter and pried up to better engage the gears thus breaking the case mount and both starter mounts plus the case mount for the sprocket cover. Maybe the problem is the starter clutch because the first day it did it I spent 10 minutes repeatedly hitting the starter until it finally started and once warm started fine but I hate to leave on a bike I can't trust to get me home. While I have it tilted I am going to pull the carbs and do a re-build and tweak anything else I see while I am in there. In the mean time I can collect a new clutch and idler gear for the inevitable case change.
Thanks.

twinegar · Post by **twinegar** » Sat Aug 29, 2009 11:12 am

There might be enough material to allow grinding out a space for a threaded bolt coupler to braze into but I still have the starter clutch and or idler gear problem. Has anyone reading this ever done a case replacement? I can pull it off if the crank and bearings can be transferred over as is.

Don · Post by **Don** » Sat Aug 29, 2009 1:05 pm

Sounds like a job for Marine-Tex - Put a blob on there, shape it as needed with a Dremel tool, drill a new hole and tap it and then spray the repair silver and remount the starter. As an alternative, you could screw a stud into what hole you have left, put a blob of Marine-Tex around it, shape it as needed to make the starter fit correctly and then mount the starter using a nut and lockwasher

http://www.marinetex.com/

You can buy it on eBay if you don't have a dealer near you

It will glue anything to anything - My hardware store had a piece of a tire carcass glued to a Coke bottle as part of their display. Thousands of guys tried to pull them apart over the 15 or 20 years they had that bottle there. It's VERY heat resistant (I patched an exhaust riser on my sailboat diesel with it) and you can drill and tap it like metal

Don

twinegar · Post by **twinegar** » Sat Aug 29, 2009 9:13 pm

That stuff sounds interesting. I have decided to change the cases and have located a set of 80 cases. I will spend the next few months collecting all the new parts I can locate to do do as close to an engine rebuild as I can get with the exception of the hard parts like crank and transmission. All case seals and all vinyl parts and valve seals. I am going to ask the same question that I asked before, this time in statement form and hopefully hear back. If a person was replacing a crank with a new one plasti-gauge would be used to install the right bearings so it makes sense to me that if a crank and bearing set from another engine were being installed in a replacement case that a simple transfer and bolt down would be all that is needed. Any comments? I am not being facetious but trying to see if I have the skill to do it.

Don · Post by **Don** » Sun Aug 30, 2009 11:06 am

You'll need to buy new main bearings . . . . and they'll have to match your new crankcase

Refer to pages 12-11 and 12-12 in the shop manual. Each crankcase is different and has each main bearing journal 'coded' . . . . they are not all the same size so each journal can require different bearing outer diameters

Take off the left crankshaft cover and you'll see the codes for the 7 main bearings from left to right - Those codes refer to the size hole bored in the case for the crank bearing. Using those codes for ther outer bearing diameters and the crankshaft main bearing journal diameters (the inside bearing measurement) you can determine which bearing is correct for each journal. Bearings come in 5 different sizes as shown in the table on page 12-12 and each size is to fit a certain combination of the diameter hole bored in the case and the diameter of the crank journal

It will all make sense when you read the shop manual, but it sure ain't like rebuilding a 350 Chevy where all crank bearings have the same outer diameter . . . . and they usually have the same inner diameter as well assuming you just had the crankshaft machined - On your CBX, you could have as many as 5 different bearings all in the same engine

So . . . . the short answer is no - You cannot just pick your crankshaft and it's current bearings up out of your old case and set them in the new case . . . . you'll need 7 new bearings and each of the 7 must be matched to the case and the particular crank journal which it will be used on

Don

cbxtacy · Post by **cbxtacy** » Sun Aug 30, 2009 11:06 am

If you look in the shop manuel there are three different values for Crank pin outside dia and three different ones for case inside dia. All together there are 5 different bearing inserts coded using color for size. The code for the crank case I.D. is located on the cases and the code for the crank pin O.D. is located on the crank. Don't confuse the rod pin codes with the main pin codes. The rod pin O.D. codes are on the crank also.

twinegar · Post by **twinegar** » Sun Aug 30, 2009 11:33 am

Thanks guys....I guess I will try to repair my cases first with Marine-Tex and if it works, replace all the internal seals and starter components. I don't know that I am up to fitting new bearings yet. Maybe I will practice on one of my spare CB750 engines first.

cbxtacy · Post by **cbxtacy** » Sun Aug 30, 2009 11:43 am

but it's not as daunting as it sounds. It's just matching up the bearings with the proper codes. You have to do the same with the rods if you change them from crank to crank. Look at the bright side, when Andreas built the V12, he turned the journals to fit 2 rods per journal. Had to turn the crank journals to move the crank over just a tad in the cases. Cases were line bored. He got the thickest bearings available, assembled averything using plastiguage, and trimmed the bearings to fit. I don't know how many times he assembled and re-assembled the engine until everything was within tolerance.

twinegar · Post by **twinegar** » Sun Aug 30, 2009 12:07 pm

I'm not afraid to do it but if I can repair the damage and replace worn parts I will be back on the road sooner. I can shelve the replacement cases and start collecting the proper bearings for a later rebuild. This is fun stuff and I have my 79 to drive in the mean time.

cbxtacy · Post by **cbxtacy** » Sun Aug 30, 2009 12:10 pm

and that is why it is important to own multiple CBX's

twinegar · Post by **twinegar** » Sun Sep 06, 2009 12:33 pm

Last night I was prepping the case for an application of Marin-Tex and discovered almost a half inch of solid threaded metal full of epoxy. Had the original bolt been longer it would probably have broken out the entire casting so I lucked out. The Marine-Tex will mostly provide a cosmetic repair with the remaining threads doing the work. Case change averted.

daves79x · Post by **daves79x** » Mon Sep 07, 2009 9:17 am

Just remember that the front starter bolt also holds your battery ground. Make sure that with your repair, you can (A) get it properly tightened for a good ground, and (B) have the bolt in contact with enough metal to provide that ground. Otherwise, I'd jumper to some other good ground with the battery wire.

Dave